Process and equipment for making simulated olive products by coextrusion, and obtainable product

ABSTRACT

Our invention is concerned with a process and equipment and the resulting product. The process and equipment produce simulated cylindrical olive products with a central core. An aqueous alginate or low-methoxy pectate sol containing dispersed olive flesh is co-extruded through a nozzle with a stream of an aqueous solution containing dissolved calcium ions flowing through an inner core of the nozzle at not more than +/−30° to the horizontal into a bath of an aqueous solution containing dissolved calcium ions. The sol of alginate or low-methoxy pectate gels by diffusion of the calcium ions from the co-extruded stream containing dissolved calcium ions and from the aqueous solution containing dissolved calcium ions in the bath. A cylindrical tube of gelled alginate or low-methoxy pectate containing pulped olive is formed with a hollow core. Preferably the sol contains a calcium salt in addition to the dispersed olive flesh which calcium salt has insufficient free ions to gel the sol but in acidic conditions is soluble and so then can gel the sol. A plurality of nozzles can advantageously be used. The density of the solution in the bath is preferably greater than the density of the extruded sol.

The present invention relates to a process to prepare simulated oliveproducts, equipment usable in such a process and related products.

It has long been recognised that processes transforming culled andotherwise wasted olives and the like to prepare simulated olive productswould be useful. For instance such simulated olive products could helpmeet the great need for olive slices for products such as pizzas and theneed for olive products e.g. as snacks.

U.S. Pat. No. 5,094,871 to Heath sets out the background showing thedemand for such processes, related equipment, and products and also thegeneral technology used in the olive industry e.g. for “curing” olivesand preparing “black ripe” style olives. U.S. Pat. No. 5,094,871 thensets out Heath's invention. This involves either a) mixing a stream ofolive flesh containing an alginate gellable by calcium ions and achelating agent such as hexametaphosphate in a high shear mixer withanother stream of olive flesh containing a calcium salt such as calciumsulphate and extruding the mixture obtained down a tube or into mouldsto allow gelation to come to completion or b) heating olive fleshcontaining a heat activated alginate and then cooling the mixture whilstit is extruded down a tube or into moulds to allow gelation to come tocompletion. In each case the mixture also contains other ingredients togive appropriate characteristics to the product. U.S. Pat. No. 5,094,871describes co-extrusion of such olive streams with other materials andmentions that, when an extruder barrel is used, a small diameterconcentric rod can be provided to give the extruded product a centrehole, which is usually desired.

The use of alginate as a gelling agent is long-established although theinteraction between the various factors involved remains relativelypoorly understood.

Another publication which proposes the use of alginate as a gellingagent in the preparation of simulated olive products is U.S. Pat. No.5,783,241 to Bocabeille et al. In one of the processes proposed in U.S.Pat. No. 5,783,241 a mixture of alginate and olive flesh is extruded asa cylinder vertically upwards into a bath containing free calcium ions.The cylinder can be hollow i.e. when a ring-shaped die orifice is used.

Our invention provides an improved process and related equipment forpreparing simulated olive products in cylindrical form with a hollowcore and also improved such products.

In our process for preparing simulated olive products in cylindricalform with a hollow core

-   -   an aqueous alginate or low-methoxy pectate sol containing        dispersed olive flesh is co-extruded through a nozzle,    -   with a stream of an aqueous solution containing dissolved        calcium ions flowing through an inner core of the nozzle,    -   at not more than +/−30° to the horizontal,    -   into a bath of an aqueous solution containing dissolved calcium        ions, to gel the alginate or low-methoxy pectate sol by        diffusion of the calcium ions, from the co-extruded stream        containing dissolved calcium ions and from the aqueous solution        containing dissolved calcium ions in the bath,    -   to form a cylindrical tube of gelled alginate or low-methoxy        pectate containing pulped olive with a hollow core.

U.S. Pat. No. 5,094,871 refers to olive meat and olive pulp. We areusing similar materials which we generically call “olive flesh” todistinguish them from stoned whole olives. The olive flesh can beparticulate or pulped. Suitable olive flesh, for example, is thatproduced by brush screening of olives to leave the stones behind, theflesh achieved by brush-screening pitted olives and the flesh that canbe removed from the stones after they have been cut out of whole olives.

Our process advantageously is especially adaptable to use with aplurality of nozzles, preferably at least four and particularlypreferably at least ten. There is no upper limit in principle butpractical considerations will usually limit the maximum to, say, twenty.

With such use of a plurality of nozzles we have found that it isimportant that the pressure at the extrusion point of the stream of theaqueous solution containing dissolved calcium ions through each innercore is both monitored and kept constant. We have found that theconstant pressure is best achieved not by the use of pumps but by theuse of a constant head of the aqueous solution containing dissolvedcalcium ions being extruded through the inner cores. Monitoring thepressure ensures that any blockages in the core liquid supply can bedetected and located quickly. Sensors for each nozzle are preferablyused. If a blockage occurs upstream of the sensor the pressuredecreases, whereas a blockage occurring downstream of the sensor willcause the pressure to decrease.

Advantageously the alginate or low-methoxy pectate together with minoringredients such as starch is dispersed in oil e.g. olive oil and thedispersion obtained is then mixed with dispersed olive flesh and water,preferably first in a low-shear bulk mixer and then in an in-linehigh-shear mixer. The high-shear mixer has to be such as to ensurehydration of the alginate without incorporating air into the system.

The aqueous solution containing dissolved calcium ions flows through theco-extruded tube of sol in part because of the head of the solution atthe extrusion point but mainly because of another feature of ourinvention: recognition that adequate flow can be achieved by the pull ofthe extruding tube of sol on the co-extruded aqueous solution containingdissolved calcium ions.

In this connection it is advantageous to ensure that the aqueoussolution containing calcium ions in the bath flows in the direction ofextrusion of the sol and at a greater rate than the rate of extrusion ofthe sol as this gives a tow to the extruded sol. The flow of the aqueoussolution in the bath is preferably constant. The rate of extrusion ofthe sol is related to the length of the bath as a residence time of atleast about 3 minutes is required to obtain adequate stability of thecylindrical tube of gelled alginate or low-methoxy pectate containingthe olive flesh with a hollow core. Our process has the advantage thatshort residence times can be achieved e.g. below 10 mins certainly below20 mins. At an extrusion rate for the sol of 5 cm/sec the length of thebath has to be at least 9 m.

In our process the gelation of the extruded tube of alginate orlow-methoxy pectate sol occurs by diffusion of calcium ions both fromthe bath of the aqueous solution containing dissolved calcium ions andalso from the aqueous solution containing dissolved calcium ions insidethe tube. Achievement of such diffusion setting in a process with othermajor advantages is the most important feature of our invention. Despitethat we do not exclude use of supplementary non-diffusion setting e.g.setting using mixing of sol with sources of calcium ions or use of e.g.heat-setting systems. However use of diffusion setting as the sole or atleast the predominate setting mechanism is much preferred.

To ensure consistent gelation of the sol it is of some importance thatthe extruded tube is subject to uniform contact with the aqueoussolution containing dissolved calcium ions. However we have found thatthe process functions best when the density of the aqueous solutioncontaining calcium ions in the bath is greater than the density of theextruded sol so that the extruded sol floats to the surface of the bath.We have found the effect of this on consistent gelation is relativelylow but in any case can be countered by bubbling air or other inert gasup from below the extruded sol to ensure the extruded sol is kept moistwith the aqueous solution containing dissolved calcium ions. This can beachieved by laying perforated tubes across the bottom of the bath atintervals down the length of the bath and at right angles to the flow ofthe aqueous solution in the bath and pumping e.g. air through thesetubes.

Preferably the aqueous alginate or low-methoxy pectate sol containingdispersed olive flesh is co-extruded with the stream of an aqueoussolution containing dissolved calcium ions at not more than +/−5° to thehorizontal, particularly preferably horizontally into the bath of anaqueous solution containing dissolved calcium ions.

Horizontal or approximately horizontal co-extrusion of alginate orlow-methoxy pectate sol and a solution containing calcium ions has aninherent disadvantage over vertical extrusion whether downwards ofupwards, e.g. as proposed by Bocabeille et al in U.S. Pat. No.5,783,241. This is that the extrudate falls or floats automatically fromthe extrusion nozzle. This can cause blocking of the nozzle and/orcreation of distorted products. In this important context we have foundthat it is advantageous to start the extrusion of the aqueous alginateor low-methoxy pectate containing dispersed olive flesh onto a supportsurface above the level of the bath containing dissolved calcium ionsand then lowering the surface into the bath whilst chopping off the endsof the extruded alginate sol at the same time beginning the co-extrusionof an aqueous solution containing dissolved calcium ions.

We have found that the exit of the inner nozzle is preferably chamferedso that the outer edge is further advanced than the inner edge.Surprisingly, this produces more even flow than with a non-chamferedinner nozzle or a chamfered inner nozzle with the inner edge furtheradvanced than the outer edge. The cross-sections of the outer alginatesol and the inner aqueous solution are maintained more uniformly. Afactor is that uneven contact of the aqueous solution of calciumchloride and the alginate sol is minimised. This use of an inner nozzlechamfered as stated is of advantage not only in connection with thepresent invention but also with other co-extrusions, particularly whenthe co-extruded systems interact together especially when physicalchange occurs because of the interaction. Of course the chamfered shapedoes not necessarily have to be produced by the physical process ofchamfering as long as the shape is obtained.

Particularly when a plurality of nozzles is used it is advantageous tocut the tubes of gelled alginate or low-methoxy pectate containing oliveflesh into segments at least 80 cm long, and preferably not longer than100 cm, and subsequently to cut these segments to shorter lengths. Thisof course should only be done when they are adequately stable.

We have found that it is advantageous to accelerate the tubes in thedirection of flow of the aqueous solution containing dissolved calciumions in the bath as they are cut. We have found an advantageous way ofachieving this: as they are cut the tubes are accelerated in thedirection of flow of the aqueous solution containing dissolved calciumions in the bath by the bath being shallower for at least 25 cm startingwithin 10 cm of the position at which the tubes are cut. The depth ofthe shallow must of course be greater than the depth of the tubes.

The tubes of alginate or low-methoxy pectate are still fragile at andafter the stage at which they are cut. For instance getting them out ofthe bath of the aqueous solution containing calcium ions is a problem.We have found that this can be achieved using a tray with sufficientcross-supports to lift them out at right angles to the direction ofextrusion.

Calcium chloride is the preferred source of calcium ions but othersoluble calcium salts can be used e.g. calcium lactate and calciumacetate monohydrate.

Aqueous alginate sol is the preferred sol. Texture can be modified byusing alginates from different seaweeds. Alginate is a linear polymercomposed of mannuronic acid (M) and guluronic acid (G). The M:G ratio,which depends on the seaweed from which the alginate is prepared,influences the texture of resulting gels. Gels which are rich inguluronic acid (high G alginates e.g. above 50% guluronic residues) tendto produce stronger gels than those rich in mannuronic acid (high Malginates). For this reason high G alginates are preferred in ourprocess. However high M alginates can be used in cases where theyprovide a more desirable texture.

When low-methoxy pectate is used it should preferably contain less than30% methoxylated hydroxyl groups. “Low methoxy pectate” is a well-knownterm. The normal dividing line between low-methoxy pectate (or pectin)and high-methoxy pectate (or pectin) is 50% methoxylated hydroxylgroups. The alginate or low-methoxy pectate sol will usually be in theform of its sodium salt but potassium or ammonium salts can be used.

That our process uses diffusion setting has been emphasised. Diffusionsetting minimises shear during gelation leading to more efficient use ofingredients and/or better, e.g. more consistent, products.

Preferably we use diffusion of calcium ions into alginate or low-methoxypectate sol. But an alternative form of diffusion setting is the use ofacid to diffuse into alginate or low-methoxy pectate sol containing adispersed calcium salt insoluble in non-acid conditions but soluble inacid conditions. In that case the alginate or low-methoxy pectate solcontains, as well as dispersed olive flesh, also a calcium salt havinginsufficient free ions to gel the sol but which in acidic conditions issoluble and so would gel the sol; and the solution co-extruded throughthe inner nozzle is an aqueous solution of an acid, preferably anaturally occurring organic acid such as citric acid, malic acid, lacticacid, tartaric acid or fumaric acid. The pH of the alginate solcontaining dispersed olive flesh can be as low as 5.5 without gelationof the sol occurring to too great an extent. Preferably it is kept inthe range 5.5 to 6 before diffusion of acid occurs to lower the pH toinitiate full gelation. Preferred sources of calcium ions are calciumcompounds which are substantially insoluble under neutral conditions butwhich become soluble under acid conditions, such as CaHPO₄ and normalcalcium tartrate.

FIGS. 1 and 2 show a diagrammatic cross-section of equipment for use inthe process according to the invention and of the process in operation.

Referring to FIG. 1, H1 is a hopper into which were poured alginatedispersed in olive oil and a mixture of pulped olives and water to givea mixture of olive flesh and aqueous alginate sol. More details of theingredients are given below. The hopper feeds to an auger-fed pump, M1,which feeds an in-line high-shear mixer, M2, from which the finelydispersed mixture of olive flesh and aqueous alginate sol was fed to sixextrusion nozzles spaced evenly apart horizontally, exemplified byextrusion nozzle, E1.

T1 is an elongated bath containing an aqueous 12% solution of calciumchloride. FIG. 1 shows only the initial 300 cm of tank, T1. The bath isabout 20 cm wide. The finely dispersed mixture of olive flesh andaqueous alginate sol was extruded from the six extrusion nozzles, e.g.E1, in the direction of flow of the aqueous solution of calcium chlorideindicated by the arrows, A1. The flow of the aqueous solution of calciumchloride was 10 cm/sec i.e. greater than the speed, 5.5 cm/sec at whichthe aqueous alginate sol containing dispersed olive flesh is extruded.

Aqueous 12% solution of calcium chloride, fed under constant pressurefrom supply tank, T2, was co-extruded through inner nozzles, e.g. E2,with the finely dispersed mixture of olive flesh and aqueous alginatesol through e.g. E1. Taps, not shown, were provided to control the flowof the solution of calcium chloride through the inner nozzles, E2. Aconstant head of 2 cm was maintained by a miniature ball-cock, notshown. Sensors, not shown, were situated at the exit points of the innernozzles, e.g. E2, to measure the pressure at those separate points.

P1 is an example of perforated pipes laid at right angles along thelength of tank, T1, and across its base. The pipes were spaced atintervals of about 200 cms along the bath. Air was passed through thesepipes to produce bubbles which splashed the aqueous 12% solution ofcalcium chloride over the just floating tubes of finely dispersed oliveflesh and aqueous alginate sol extruded through the nozzles, e.g. E1.The extruded tubes are shown in FIG. 2 rather than in FIG. 1. For eachextruded tube, vertical rod guides, not shown, were fixed in the bath.There were six spaced evenly down the bath. The gap between the guiderods for the tubes was about 3 cm.

The overall formulation was as follows:

% Olive/water stream Pulped olive 45.0 Water 45.0 Sodiumhexametaphosphate 0.5 (The sodium hexametaphosphate is present tochelate any calcium ions in the mixture of olives and water.) Alginatestream Liquid vegetable oil 2.5 Alginate (Manugel DPB*) 2.0 Starch(Instant Clearjel*) 4.0 Cellulose filler (Solka floc*) 1.0 100 *ManugelDPB is a trade mark of ISP Alginates and obtainable from ISP (Alginates)UK. Manugel DPB is a high G alginate. *Instant Clearjel is a trade markof National Starch. *Solca Floc is a trade mark of International FibreCorporation, Tonawanda, New York, USA.

Referring to FIG. 2: this shows only the final 300 cms of tank, T1. Thetotal length of tank, T1, is 1400 cm. The just-floating tubes of finelydispersed olive flesh and aqueous alginate sol referred to above areshown in FIG. 2 as, e.g., TB1. The tubes moved in the direction of thearrows, A2. A guillotine with a cutting edge, GC1, and a block, GB1, cutthe tubes, e.g. TB1, into segments, e.g. TS1 The base of the bath israised, AZ1, to accelerate the flow of the aqueous solution of calciumchloride and hence the flow of the tubes, e.g. TB1, as shown by arrowsA3. This acceleration helped keep the segments, e.g. TS1, apart. Thenormal depth of the bath is 10 cm. The depth where the base is raised is2.5 cm so the velocity of the bath liquor in the shallow part was 4times the velocity in the normal part.

A perforated tray, TR1, lifted the segments, e.g. TS1, from the bath andtipped them into a bath of water, not shown. The densities of the tubesand of the water were roughly equal. Tubes were removed for furtherprocessing from the lower levels of the bath of water on a “first-in,first-out basis”; in-coming tubes pressed tubes already in the bath ofwater down in the bath. The residence of the tubes in the bath of waterwas about ½ hour.

The aqueous 12% calcium chloride solution flowed over a weir, W1, at theend of the bath, T1, into a hopper, H2, from which it flowed to a supplytank, T3, shown in FIG. 1, from which it was supplied to the bath asshown in FIG. 1 and, although not shown, to the constant head supplytank, T2. The initial concentration of calcium chloride was restored,when required, by addition of calcium chloride to the supply tank, T3.

The process was run at ambient temperature, i.e. 20° C., forconvenience.

Percentages are by weight unless otherwise indicated.

1. A process for preparing simulated cylindrical olive products with ahollow central core comprising extruding an aqueous alginate sol oraqueous low-methoxy pectate sol containing dispersed olive flesh througha nozzle inclined at not more than +/−30° to the horizontal which nozzlecontains an inner nozzle and simultaneously extruding a stream of anaqueous solution containing dissolved calcium ions through the innercore of the nozzle, into a bath of an aqueous solution containingdissolved calcium ions, and gelling the aqueous alginate sol or aqueouslow-methoxy pectate sol by diffusion of the calcium ions from theco-extruded stream of the aqueous solution containing dissolved calciumions and from the aqueous solution containing dissolved calcium ions inthe bath, thereby forming a cylindrical tube of gelled alginate orgelled low-methoxy pectate containing dispersed olive flesh with ahollow core.
 2. A process according to claim 1 in which a plurality ofnozzles containing inner nozzles is used to produce a plurality ofcylindrical tubes of gelled alginate or gelled low-methoxy pectatecontaining dispersed olive flesh with hollow cores.
 3. A processaccording to claim 2 in which the density of the aqueous solution in thebath is greater than the density of the aqueous alginate sol or aqueouslow-methoxy sol extruded from the nozzles.
 4. A process according toclaim 3 in which the aqueous solution in the bath flows in the directionof extrusion of the sol and at a greater rate than the rate of extrusionof the sol.
 5. A process according to claim 1 in which the pressure ofthe simultaneously extruded stream of the aqueous solution containingdissolved calcium ions is monitored at the point it is extruded into thebath of the aqueous solution containing dissolved calcium ions.
 6. Aprocess according to claim 5 in which the pressure of the simultaneouslyextruded stream of the aqueous solution containing dissolved calciumions is kept constant at the point it is extruded into the bath of theaqueous solution containing dissolved calcium ions.
 7. A processaccording to claim 4 in which the tubes of gelled alginate or gelledlow-methoxy pectate containing dispersed olive flesh are initially cutinto segments which are at least 80 cm long and subsequently thesegments which are at least 80 cm long are cut to lengths shorter than80 cm.
 8. A process according to claim 7 in which as the tubes areinitially cut the tubes are accelerated in the direction of flow of theaqueous solution in the bath.
 9. A process according to claim 8 in whichas the tubes are initially cut the tubes are accelerated in thedirection of flow of the aqueous solution in the bath by the bath beingformed shallower for at least 25 cm starting within 10 cm downstream ofwhere the tubes are cut.
 10. A process according to claim 3 in which airor other inert gas is bubbled up from below the extruded aqueousalginate sol or the aqueous low-methoxy pectate sol thereby ensuringthat the extruded aqueous alginate sol or aqueous low-methoxy pectatesol is kept moist with the aqueous solution containing dissolved calciumions in the bath.
 11. A process according to claim 1 in which theprocess is started by extruding the aqueous alginate sol or aqueouslow-methoxy pectate sol containing dispersed olive flesh onto a supportsurface above the level of the aqueous solution containing dissolvedcalcium ions in the bath and then the support surface is lowered intothe bath whilst chopping off the ends of the extruded aqueous alginatesol or aqueous low-methoxy pectate sol at the same time as startingsimultaneously extruding the stream of the aqueous solution containingdissolved calcium ions through the inner core of the nozzle.
 12. Aprocess according to claim 1 in which the nozzle containing an innernozzle is inclined at not more than +/−5° to the horizontal.
 13. Aprocess according to claim 12 in which the nozzle is horizontal.
 14. Aprocess according to claim 3 in which the cylindrical tubes of gelledalginate or gelled low-methoxy pectate containing dispersed olive fleshwith hollow cores are removed from the bath using a tray with sufficientcross-supports to lift the tubes out of the bath at right angles to thedirection of extrusion.
 15. A process according to claim 1 in which theexit of the inner nozzle is chamfered so that the outer edge is furtheradvanced than the inner edge.
 16. A process according to claim 1 inwhich the stream of an aqueous solution containing calcium ions and theaqueous solution containing dissolved calcium ions in the bath arereplaced by aqueous solutions containing dissolved acid and the aqueousalginate sol or aqueous low-methoxy pectate sol containing dispersedolive flesh also contains a dispersed insoluble calcium salt insolublein non-acid conditions but soluble in acid conditions.
 17. A processaccording to claim 1 in which the sol is an alginate sol.
 18. A processaccording to claim 17 in which the alginate is a high G alginate.